What problem does it solve? Hard bugs and performance regressions stall when developers jump straight to hypotheses without a reproducible signal. This Skill enforces a disciplined diagnosis loop that builds a tight pass/fail feedback signal first, then reproduces, minimizes, hypothesizes, instruments, fixes, and cleans up. ## Core Features & Use Cases - Feedback loop construction: Builds a red-capable, deterministic, fast reproduction command using failing tests, curl scripts, CLI fixtures, headless browser scripts, trace replays, fuzz loops, or bisection harnesses. - Structured hypothesis testing: Generates 3-5 ranked falsifiable hypotheses, then instruments with tagged debug logs or debugger breakpoints, changing one variable at a time. - Regression testing and post-mortem: Writes the regression test before the fix at a correct seam, removes all debug instrumentation, and documents the confirmed root cause. - Use Case: A user reports that an export endpoint intermittently returns corrupted data. The Skill guides building a loop that replays the failing request 100 times, minimizes the repro, tests ranked hypotheses, and lands a fix with a regression test. ## Quick Start Diagnose this bug: the export endpoint intermittently returns corrupted JSON, and build a reproduction loop before proposing any fix.
